The general goal of the proposed research is to illuminate the relationship between neuronal activity and auditory function. Specifically we are interested (1) what are the psychophysical abilities of human and non- human subjects in integrating spectral and temporal features of sounds, and (2) how do auditory cortical single neuron responses relate to this ability as measured through psychophysical performance. Psychophysical measurements will be made from human and non-human subjects to determine their ability to discriminate temporally or spectrally complex sounds. We will then record single unit responses from non- human subjects while they discriminate sounds used in the psychophysical experiments. For one aim, we will investigate amplitude modulation as a function of sound duration and AM frequency and for the other aim investigate complex sound spectra. Using novel modifications of signal detection theory, we will determine the discriminative capabilities of neurons, and whether the firing of individual neurons is more closely associated with the physical attributes of sound or to the pscyhophysicaljudgement. These results will provide critical direct links between single neuron physiological function and psychophysical perfrormance. This data will add knowledge about the effects of cortical disruptions due to strokes trauma, and other degenerative diseases of the brain on hearing. Additionally, this study should add to the understanding of temporal acoustical processing which appears related to many of the effects of dyslexia and other developmental disorders. These results accordingly are of potential use for understanding and treating strokes and developmental disorders. Achieving the three aims will allow us to rigorously assess: (1) how spectral and temporal information is integrated and combined by the auditory central nervous system.